Ashwagandha (Withania somnifera) is a root long used in Ayurvedic medicine and now one of the most widely sold “adaptogen” supplements worldwide, marketed for stress relief, anxiety, and sleep support. Interest has grown alongside a substantial body of clinical research over the past decade, but the evidence on both its benefits and its risks is more nuanced than most marketing suggests. This article reviews what current research actually shows.
What ashwagandha is and how it is thought to work
Ashwagandha is a shrub whose root and, increasingly, leaf extracts are used in supplements. It contains phytochemicals called withanolides, which are believed to be responsible for many of its proposed effects, along with other compounds that may also play a role (Office of Dietary Supplements, 2025). It is classified as an “adaptogen,” a term used for substances thought to help the body resist and adapt to physical and psychological stress, in part by influencing the hypothalamic-pituitary-adrenal (HPA) axis and cortisol regulation (Lucius, 2025).
Evidence for stress and anxiety
This is where ashwagandha’s evidence base is strongest. Multiple systematic reviews and meta-analyses of randomized controlled trials have found consistent, statistically significant reductions in perceived stress and anxiety scores compared with placebo:
- A meta-analysis of nine randomized controlled trials involving 558 participants found a significant reduction in Perceived Stress Scale (PSS) scores among those taking ashwagandha compared with placebo (PubMed, 2022, as cited in study abstract).
- A more recent meta-analysis (15 studies, 873 participants) similarly found significant reductions in stress and anxiety measures across trials (PMC, 2024).
- A 2025 randomized, double-blind, placebo-controlled trial of a low-dose ashwagandha formulation (125 mg/day) over 84 days found significant improvements in perceived stress, mood, and sleep quality compared with placebo, alongside physiological markers such as heart rate variability (Mahadevan et al., 2025).
- However, a separate systematic review focused specifically on cortisol found a more mixed picture: ashwagandha reliably lowered cortisol levels in trials, but this biological change did not always translate into a significant improvement in perceived stress scores, highlighting a gap between physiological and subjective outcomes (Singh et al., as cited in Lucius, 2025).
Taken together, the evidence for short-term (typically 4–12 week) use in reducing perceived stress and anxiety is among the more consistent findings in the herbal supplement literature, though most trials remain relatively small and short in duration.
Evidence for sleep
Ashwagandha’s effect on sleep has also been studied directly, with generally positive but modest results:
- A systematic review and meta-analysis of five randomized controlled trials (400 participants) found a small but statistically significant improvement in overall sleep with ashwagandha compared with placebo, including benefits for sleep onset latency, total sleep time, wake time after sleep onset, and sleep efficiency (PLOS One, 2021).
- These sleep benefits were more pronounced in adults who had diagnosed insomnia, and were more consistent at treatment doses of 600 mg per day or higher, sustained for eight weeks or longer (PLOS One, 2021).
- A National Institutes of Health–reviewed trial of a standardized root-and-leaf extract given to 150 adults with self-reported sleep problems over six weeks found improvements versus placebo (Office of Dietary Supplements, 2025).
- A 2025 double-blind trial of a low-dose formulation reported improved sleep quality alongside reductions in stress and anxiety symptoms over 12 weeks (Mahadevan et al., 2025).
Overall, ashwagandha appears to modestly improve sleep quality and duration, particularly for people with existing sleep difficulties, though the effect size is smaller than that seen with medications specifically designed for insomnia.
Dosage used in research
There is no single officially established dose, since ashwagandha is regulated as a dietary supplement rather than a medication. However, clinical trials showing benefit for stress and sleep have generally used:
- Root extract: Commonly 300 mg to 600 mg per day, taken in one or two doses, most often standardized to a specific withanolide content (PLOS One, 2021; PMC, 2024).
- Lower-dose specialty formulations: Some newer trials have tested doses as low as 125 mg per day of concentrated formulations and still found benefit, suggesting extract concentration and standardization matter as much as raw milligram amount (Mahadevan et al., 2025).
- Duration: Most positive trials ran for 6 to 12 weeks; there is limited controlled research on continuous use beyond about three months (WellzRx, 2025).
Because products vary widely in the plant part used (root versus leaf versus mixed), extraction method, and withanolide concentration, the same milligram dose can vary considerably in potency between brands.
Risks and safety concerns
Ashwagandha has a long history of traditional use and is generally well tolerated in most clinical trials, but it is not risk-free, and several concerns have emerged more clearly in recent case reports and safety reviews.
Common, mild side effects
The most frequently reported side effects across trials are digestive upset (nausea, diarrhea, abdominal discomfort), drowsiness, and headache, most of which are mild and self-limited (The Mighty, 2026; PMC, 2026).
Liver injury
This is the most significant safety signal to emerge in recent years. Case reports have documented ashwagandha-associated liver injury, including jaundice and markedly elevated liver enzymes, generally arising within two to twelve weeks of use, though one case involved use for about a year (Examine, n.d.; PMC, 2023). In most reported cases, liver function returned to normal after stopping the supplement, but the pattern has been consistent enough that the UK’s Food Standards Agency asked its Committee on Toxicity to formally review ashwagandha’s safety, citing an increasing number of reported incidents (ADS, 2025). It is worth noting that large randomized controlled trials and meta-analyses of clinical trial data have generally not detected liver toxicity signals at typical trial doses, so this risk appears to be uncommon but real, and may relate to idiosyncratic individual reactions, higher doses, non-root formulations, or longer duration of use (Kerry, 2024; ADS, 2025).
Thyroid effects
Ashwagandha has been shown in some studies to increase thyroid hormone levels, and case reports have described thyrotoxicosis (an overactive thyroid state) associated with its use, although these effects have not been consistently replicated in larger trials (Examine, n.d.). Because of this, people with hyperthyroidism or those taking thyroid medication are generally advised to avoid ashwagandha or use it only under medical supervision (WellzRx, 2025).
Pregnancy and breastfeeding
Ashwagandha is not recommended during pregnancy. Traditional and some modern evidence suggests it may increase the risk of miscarriage, and there is insufficient safety data to support its use during breastfeeding (WellzRx, 2025).
Autoimmune conditions
Because ashwagandha may stimulate immune activity, it is generally advised against for people with autoimmune diseases such as lupus or rheumatoid arthritis, as it could theoretically worsen symptoms (WellzRx, 2025).
Drug interactions
Ashwagandha may interact with:
- Sedatives and sleep medications, potentially increasing drowsiness
- Thyroid medications, by further raising thyroid hormone levels
- Immunosuppressants, due to potential immune-stimulating effects
- Medications for diabetes or blood pressure, due to possible effects on blood sugar and blood pressure regulation (WellzRx, 2025; ADS, 2025)
People taking any prescription medication, particularly for these conditions, should talk to a healthcare provider before starting ashwagandha. It is also generally recommended to stop ashwagandha at least two weeks before scheduled surgery because of possible interactions with anesthesia (WellzRx, 2025).
Limited long-term data
Most clinical trials evaluating ashwagandha’s safety have lasted three months or less. There is limited controlled research on continuous daily use over periods of a year or longer, which is relevant given that some liver injury case reports have involved more prolonged use (WellzRx, 2025; MDPI, 2025).
Who should be cautious or avoid it
Based on the safety literature reviewed above, ashwagandha is generally best avoided, or used only with medical supervision, by:
- Pregnant or breastfeeding individuals
- People with hyperthyroidism or thyroid conditions on medication
- People with autoimmune diseases
- People with existing liver or kidney disease
- People taking sedatives, thyroid medication, immunosuppressants, or diabetes/blood pressure medications
- Anyone scheduled for upcoming surgery
Practical takeaways
- Ashwagandha has reasonably consistent evidence for modestly reducing perceived stress and anxiety, and for improving sleep quality in people with existing sleep difficulties, generally over 6–12 week trial periods.
- Most studied doses range from roughly 125 mg to 600 mg per day of standardized extract; higher doses (≥600 mg/day) show the clearest sleep benefits in trials.
- Mild digestive upset and drowsiness are the most common side effects.
- Rare but documented cases of liver injury and thyroid disruption warrant caution, particularly with higher doses or extended use, and product quality and standardization vary significantly between brands.
- It is not recommended during pregnancy and should be avoided or used only with medical guidance in people with thyroid disease, autoimmune conditions, liver or kidney problems, or those on interacting medications.
- Long-term safety data (beyond about three months of continuous use) remains limited.
Disclaimer: This article is for general educational and informational purposes only and does not constitute medical advice. It is not a substitute for professional medical diagnosis, treatment, or guidance. Always consult a qualified healthcare provider before starting, stopping, or changing any supplement, including ashwagandha, particularly if you are pregnant or breastfeeding, have a thyroid or autoimmune condition, have liver or kidney disease, or take prescription medication. Seek prompt medical attention if you experience symptoms such as jaundice (yellowing of the skin or eyes), dark urine, or unusual fatigue while taking ashwagandha.
References
ADS. (2025). P26-04 Review of the safety of Ashwagandha (Withania somnifera (L.) Dunal) in food, drinks and food supplements. Toxicology Letters. https://ui.adsabs.harvard.edu/abs/2025ToxL..411S.326T/abstract
Examine. (n.d.). What are ashwagandha’s main drawbacks? https://examine.com/faq/what-are-ashwagandhas-main-drawbacks/
Kerry. (2024). Ashwagandha – Is it safe? A toxicologist’s perspective. https://egrove.olemiss.edu/cgi/viewcontent.cgi?article=1072&context=icsb
Lucius, K. (2025). Clinical evidence for the use of ashwagandha, Withania somnifera. Integrative and Complementary Therapies. https://journals.sagepub.com/doi/abs/10.1089/ict.2025.28106.kl
Mahadevan, M., Gopukumar, K., Gupta, R., et al. (2025). A new ashwagandha formulation (Zenroot™) alleviates stress and anxiety symptoms while improving mood and sleep quality: A randomized, double-blind, placebo-controlled clinical study. Advances in Therapy, 42, 5238–5254. https://doi.org/10.1007/s12325-025-03327-z
MDPI. (2025). Ashwagandha (Withania somnifera) and its effects on well-being—A review. Nutrients, 17(13), 2143. https://www.mdpi.com/2072-6643/17/13/2143
Office of Dietary Supplements. (2025). Ashwagandha: Is it helpful for stress, anxiety, or sleep? Health professional fact sheet. National Institutes of Health. https://ods.od.nih.gov/factsheets/Ashwagandha-HealthProfessional/
PLOS One. (2021). Effect of ashwagandha (Withania somnifera) extract on sleep: A systematic review and meta-analysis. PLOS ONE. https://journals.plos.org/plosone/article?id=10.1371%2Fjournal.pone.0257843
PMC. (2023). Liver dangers of herbal products: A case report of ashwagandha-induced liver injury. PubMed Central. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10002162/
PMC. (2024). Effects of ashwagandha supplements on cortisol, stress, and anxiety levels in adults: A systematic review and meta-analysis. PubMed Central. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12242034/
PMC. (2026). Evaluating the safety of ashwagandha as a food additive: A focus on reproductive, thyroid, and immune system effects. PubMed. https://pubmed.ncbi.nlm.nih.gov/41454545/
The Mighty. (2026). Ashwagandha side effects: What research actually shows. https://themighty.com/topic/hypothyroidism-underactive-thyroid-disease/ashwagandha-side-effects/
WellzRx. (2025). Who should not take ashwagandha extract? Risks, side effects. https://wellzrx.com/who-should-not-take-ashwagandha-extract-a-comprehensive-guide-to-risks-and-contraindications
